fix spring between two molecules

Good day everybody,

My problem is the following. I would like to fix ~10000 springs between ~3000
groups of atoms. The problem is obvious: LAMMPS doesn't allow to define more
than 32 groups. In previous discussions I read that I can't increase the number
of groups in any simple way. I also read that is possible to solve this problem
defining each group as a different molecule and then fixing a spring between
molecules. Nevertheless the "fix spring couple" command needs the IDs of 2
groups.

Does anybody know how I can fix a spring between 2 molecules instead of 2
groups?

Thanks

Best Regards
Marco

Good day everybody,

My problem is the following. I would like to fix ~10000 springs between ~3000
groups of atoms. The problem is obvious: LAMMPS doesn't allow to define more

now here is an unusual idea...

than 32 groups. In previous discussions I read that I can't increase the number
of groups in any simple way. I also read that is possible to solve this problem
defining each group as a different molecule and then fixing a spring between
molecules. Nevertheless the "fix spring couple" command needs the IDs of 2
groups.

Does anybody know how I can fix a spring between 2 molecules instead of 2
groups?

applying fix spring for this kind of purpose
would for certain be horribly inefficient.

without knowing more about the way how those
springs should be applied it is difficult to make
any specific recommendations. is there a simple
rule how those springs are supposed to be applied?
perhaps, this could be expressed in a custom pair
style? or a bond/angle/dihedral style?

axel.